Cushion material formed of spring-structured resin-molded product, manufacturing method for the cushion material, and mold used for the manufacturing method

ABSTRACT

There is provided a method for producing a cushion material composed of a resin molded article with a spring structure which is so moldable as to allow the mold take any shape and size, is cheap, and resistant to collapsing, does not cause fatigue even after prolonged use, and has high shock absorbing capability and load capacity, and thus suitably used as a material of any supports on which one can sit, rest or mount such as seats of automotive vehicles, motor cycles, bicycles, electric trains, and aircraft, saddles for horse riding, chairs, sofas and beds, and a method for producing a cushion material requiring only a low cost for its disposal.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a cushion material composed of a resinmolded article having a spring structure, method of producing the same,and dies used in manufacture of the cushion material, more particularlyto a method for producing a resin molded article with a spring structurewhich is excellent in shock resistance and load capacity, and has anability to meet specific and non-specific needs in terms of shape andsize in various industrial fields, that is, a material suitably used forproducing any supports on which one can sit, rest or mount such as seatsof automotive vehicles, motor cycles, bicycles, electric trains, andaircraft, saddles for horse riding, chairs, sofas and beds, and to amethod for producing a cushion material which requires a low cost andburden for its disposal, and low production cost by simplifyingproduction facilities, and improves the precision of molding, andapparatuses necessary for producing the cushion material.

2. Background Art

At present, a polyurethane foam is a mainstream material of cushions forseats and beds of automotive vehicles, motor cycles, bicycles, electrictrains and aircraft. Generally, cushions are used in some form oranother in any supports on which one can sit, rest or mount regardlessof whether they are exposed to vibrations during use or not. Indeed,polyurethane foam is widely used in various applications, and the widespread of this material is ascribed to its being comparatively free fromproblems in production and cost.

One of such cushion materials is disclosed, for example, in JapanesePatent No. 2995325 which proposes a cushion pad for the seat ofautomobiles. Of the cushion pad in question, a seat surface part isformed of a high resilience foam having a one layer structure, and thehigh resilience foam is made of a polyurethane foam which contains 10 wt% or less of tolylene diisocyanate (TDI), and the remainder isocyanateformed by diphenylmethane diisocyanate. Japanese Patent No. 2548477proposes a cushion structure obtained by fusing polyester fibers with ahigh melting point to each other via a thermoplastic elastomer with alow melting point. A cushion is proposed in Japanese Laid-Open PatentPublication (Kokai) No. 2000-51011, which is obtained by partiallybonding synthetic fibers and natural fibers of 1 to 20 deniers with eachother, via a synthetic rubber adhesive or cross-linking polyurethane.

Generally, when a man sits on a seat made of polyurethane foam, hisweight tends to concentrate in one point so much that polyurethane foambeneath the point sinks deeply. Thus, his balance becomes unstable, andhe gets fatigued if he sits on the seat for a long time. The main reasonfor this is as follows. Manufacture of a product of a polyurethane foamis achieved by placing a foaming material in a mold, and foaming thematerial uniformly, to give a product uniform in density and strength.With this manufacture it is difficult to obtain a product of which partsare modified in density and strength according to the functions they areassigned. Furthermore, because polyurethane foam is so soft and elasticthat, when man rests his weight on a seat made of polyurethane foam, hefeels an upward thrust on his buttock, touching on a hard bottom, andvertical swing, and his feet may become numb and strongly tired if herests on the seat for a long time. Take a polyurethane seat for a car ormotorcycle as an example. Demands with regard to the manufacture andstructure of such a polyurethane seat are manifold, but the materialitself is so uniform in density that, when a man sits on the seat, thedistribution of pressures on the sitting surface changes from moment tomoment, and thus polyurethane foam may not be suitable according togiven functions assigned to the seat. Manufacture of products of apolyurethane foam is generally achieved via blow foaming, and thus theproduct has a uniform spring property, or is conferred a number ofroughly different spring properties. Therefore, it is difficult for theproduct of polyurethane foam to change its spring properties inaccordance with given requirements. The seat of a motor cycle mustchange its spring property according to the type of motor cycle, e.g.,according to whether the motor cycle is for touring, road racing ormotocross, or to the rider's posture during riding. As it is, becausethe seat cannot change its spring property according to the type ofmotor cycle or to the rider's posture, the rider must put or lift hisweight on or off the seat as needed during racing, which, when repeatedoften over a long time, will cause the overall center of gravity to beelevated and unbalanced.

Further, it is difficult to recycle polyurethane foams since they arethermosetting resins. Therefore, polyurethane foams can only be recycledby crushing them into chips with a crusher, and bonding the chips into amaterial called chip foam (ribbon dead foam), or can only be burned forrecovery of thermal energy. The method of disposal of polyurethane foamsincludes landfilling and incineration. However, stable lands cannot becreated by using polyurethane foams since they are low in bulk densityand soft, and hence landfill sites suitable therefor are limited.Polyurethane foams may be processed into particles or powders to bedisposed which requires, however, extra handling and costs. Further,incineration of polyurethane foams may generate hydrocyanic acid gases(hydrocyanic acid) which cause much damage to incinerators, and have tobe eliminated at high costs. As described above, it is difficult todispose polyurethane foams in accordance with the Recycle Act withoutgiving adverse side effects on environments during and after disposal.

In addition to above, polyurethane foams have problems as describedbelow.

Manufacture of a polyurethane foam mold is achieved by blowing a foamingmaterial in a die (for example, for three minutes) and separating themold from the die. The separation process is complicated and moldingtime is long. It is difficult to clean polyurethane foams. This isbecause an amine catalyst used during manufacture is trapped in thefoams, causing bad smell. A polyurethane foam has a heat storageproperty, and is liable to be stuffy, and there is a fear that if thepolyurethane foam is exposed to intensive light for a long time, it maystart to burn. Its safety to environments is low.

Although year 2020 is set to a deadline of abolition of use of CFCs(chlorofluorocarbons) substitute which is used as a foaming agent, thereis not yet found an alternate agent that is more excellent in foamingperformance than the CFCs substitute. TDI (tolylene diisocyanate) whichis an isocyanate normally used for producing soft polyurethane foams isa very harmful material and Notification No. 25 of the Ministry of Laborof Japanese Government prescribes that TDI should be used at aconcentration of 0.005 ppm or less. In many actual manufacturing sites,thorough control of TDI is not carried out, causing damage to health ofworkers.

The above-mentioned seat cushion pad for an automotive vehicle disclosedin Japanese Patent No. 2995325 is improved in the characteristics of thesoft polyurethane foam, but still has the drawbacks of polyurethanefoams. In the cushion structure proposed in the Japanese Patent No.2548477, it is difficult to be recycled due to fusing polyester fiberswith a high melting point via a thermoplastic elastomer with a lowmelting point, resulting in complicated manufacturing method and highcost for producing. Although the cushion proposed in Japanese Laid-OpenPatent Publication (Kokai) No. 2000-51011 offers advantages in that ithas excellent air permeability and is cleanable, it suffers fromdisadvantages in that it has a low durability, a manufacturing methodthereof is complicated, and a processing cost is remarkably high.Further, since the rubber adhesive and a crosslinkable polyurethane arethermoset resins, and the cushion is not of a single composition, it isdifficult to recycle the cushion.

At present, however, despite that polyurethane foams have many problemsas described above, there is no alternate agent to replace polyurethanethat can be used not less suitably and cheaply than polyurethane as acushion material of the seats of automotive vehicles, motor cycles,bicycles, electric trains, and aircraft, and of beds.

DISCLOSURE OF INVENTION

In view of above, an object of the present invention is to provide amethod for producing a cushion material composed of a resin moldedarticle with a spring structure, that is, a material suitably used forproducing any supports on which one can sit, rest or mount such as seatsof automotive vehicles, motor cycles, bicycles, electric trains, andaircraft, saddles for horse riding, chairs, sofas and beds. To put itmore specifically, the object of the invention is to provide a methodfor producing a molded article which simplifies molding process, permitsthe manufacture of a mold comparatively freely in shape and size,requires a small cost for production, and readily produces a cushionwhich satisfies widely different requirements offered to springyarticles such as: being resistant to sinking and, when a user sits onit, being capable of dispersing his weight uniformly over the sittingsurface so that it does not fatigue the user even if he sits on it for along time, and which is excellent in shock resistance and load capacity.Particularly, the object of the invention is to provide a method forproducing a molded article which simplifies production facilities,lowers production cost, improves the precision of molding, reduces worksrequired for processing, and can provide finished products in which endsof the product will not disintegrate of themselves even withoutdeliberately resorting to trimming or rounding-off after molding.

SUMMARY OF THE INVENTION

To attain the above objects, the method of this invention for producinga cushion material composed of a resin molded article with a springstructure comprises the steps of forming a three-dimensional structureincluding voids at a predetermined bulk density which is obtained bycontacting, entwining, and gathering adjacent ones of random loops orcurls of continuous and/or short, solid and/or hollow filaments madefrom a thermoplastic resin; heating the three-dimensional structureplaced in a female die directly and/or via the die to a temperaturesufficiently high to soften the three-dimensional structure; compressingthe three-dimensional structure by bringing a male die in tight contactwith the female die; and hardening the three-dimensional structure bycooling.

The method preferably further comprises a step of removing superfluousends of the three-dimensional structure protruding into strokes betweenthe male and female dies using a heat cutter, to thereby thermally fusethe ends as well as to cut them off.

The “continuous and/or short filaments” preferably includes filamentsmade from general purpose plastics (polyolefins, polystyrene resins,methacryl resins, poly vinyl chloride, etc.) or engineering plastics(polyamide, polycarbonate, saturated polyester, polyacetal, etc.). Forexample, they are preferably made from thermoplastic elastomers such aspolyethylene (PE hereinafter), polypropylene (PP hereinafter), andnylon.

Particularly, the filaments are preferably made from a mixture obtainedby adding a vinyl acetate resin (VAC hereinafter), ethylene vinylacetate copolymer (EVA hereinafter), or styrene butadiene styrene (SBShereinafter) to a polyolefin resin such as PE or PP. The mixture ratioof the vinyl acetate content of the polyolefin resin to VAC or EVA is 70to 97 wt % to 3 to 30 wt %, preferably 80 to 90 wt % to 10 to 20 wt %.If the VAC content were equal to or lower than 3 wt %, the impactresilience of the three-dimensional structure would be low. On thecontrary, if the VAC content were equal to or higher than 30 wt %, thethermal characteristics of the structure would be degraded. The mixtureratio of the polyolefin resin to SBS is 50 to 97 wt % to 3 to 50 wt %,preferably 70 to 90 wt % to 10 to 30 wt %. The polyolefin resin may be aregenerated resin.

“The continuous and/or short filaments” may be solid or hollow. If thecontinuous and/or short filaments are hollow, they are preferablebecause the air is entrapped in the hollow cavities of the filaments,and act as a spring which confers a characteristic spring property tothe filaments. The air entrapped in the hollow cavities of the filamentsalso prevents the collapsing tendency of the filaments which wouldotherwise result from long and habitual use. The air entrapped in thehollow cavities of the filaments also preserves the rigidity of thethree-dimensional structure. The hollow cavities may be continuous withother ones or may be independent of each other. As one illustrativeexample, each of single hollow fibers may have hollow cavities withsepta inserted between adjacent cavities. If a mixture of solidfilaments and hollow filaments is used as a material of the filaments,the mixture ratio of solid filaments to hollow filaments is preferablysolid:hollow=0 to 50:50 to 100. Further, if hollow filaments are used ina central portion of the structure, and covered with solid ones, theresulting structure will give a desirable tactile impression.

The “solid continuous filaments and/or short filaments” preferably havea diameter of 0.3 to 3.0 mm, particularly 0.7 to 1.0 mm. If the solidcontinuous filaments have a diameter equal to or smaller than 0.3 mm,the filaments would lose resiliency and fuse to each other so stronglythat their void ratio would become undesirably low. On the contrary, ifthe solid continuous filaments have a diameter equal to or larger than3.0 mm, the filaments would become so resilient that they would not formloops and curls, nor fuse together, which would lead to the loweredstrength. If the filaments include hollow filaments, they preferablyhave a diameter of 1.0 to 3.0 mm, particularly 1.5 to 2.0 mm. If thevoid ratio were equal to or lower than 10%, the hollow filaments wouldlose the merit of reducing the weight of the product relative to itsbulk. On the contrary, if the void ratio were equal to or higher than80%, the hollow filaments would lose their cushioning activity.

The bulk density of the “resin molded article with a spring structure”may be 0.005 to 0.08 g/cm³, preferably 0.02 to 0.06 g/cm³. If the bulkdensity in question were 0.005 g/cm³ or lower, the article would have areduced strength. On the contrary, if the bulk density in question were0.08 g/cm³ or higher, the filaments would lose the merit of reducing theweight of the article with respect to its bulk. The resin molded articlewith a spring structure may have a uniform density throughout itsstructure or may have a structure where high density and low densitysubstructures repeat alternately at certain intervals. In the lattercase, the low density substructure may have a density of 0.005 to 0.03g/cm³, preferably 0.008 to 0.03 g/cm³, most preferably 0.01 to 0.03g/cm³. The high density substructure may have a density of 0.03 to 0.08g/cm³, preferably 0.04 to 0.07 g/cm³, most preferably 0.05 to 0.06g/cm³.

The void ratio of the “resin molded article with a spring structure” maybe 96 to 99%, preferably 97 to 99%, most preferably 97 to 98%. Tomaintain elasticity and strength of the structure as a cushion as wellas reduce the weight thereof, the void ratio in question should be inthe range as mentioned above.[void ratio (%)]=(1−[bulk density]/[density of resin])×100

The “cushion material” is preferably obtained by laminating multipleresin molded articles with a spring structure into a layered structure.The cushion material is preferably used as a material of the seats ofautomotive vehicles, motor cycles, bicycles, electric trains andaircraft, saddles for horse riding, chairs, sofas and beds. The cushionmaterial may be used, in place of urethane foams, as a material of anysupports on which one can sit, rest or mount regardless of whether theyare exposed to vibrations or not.

Particularly, when the cushion material is used as a material of theseat of an automotive vehicle or motor cycle which is exposed tovigorous vibrations during use, it is preferred because it readilyadapts to various individual requirements (e.g., suspensioncharacteristic) of the vehicle because of its thickness beingsusceptible to external controls.

The “female die” is preferably made of concrete. The concrete diedispenses with the use of a separating agent, and thus reduces the costof molding. The “male die” preferably consists of a product (base) towhich the cushion material can be attached. Then, need for separatepreparation of a male die can be safely avoided, which will allow themolding cost to be reduced, and precision of molding to be improved.Cooling may consist of spontaneous cooling or forced cooling. Forcedcooling is preferably based on the use of water.

The cushion material of the invention is more receptive to secondaryprocessing than polyurethane, and can respond to needs from consumerswith regard to particular functions more finely than polyurethane.Molding the cushion material is achieved by compression molding. Thus,it is possible to provide a product to match with the body shape of agiven user, or in accordance with the order of a user which will furtherenhance the advantage of the product. Moreover, by adjusting thediameter of filaments constituting a resin molded article with a springstructure, material of the filaments, and their denier, bulk density andvoid ratio, it is possible to allow the resin molded particle to have adesired spring property. Although individual filaments constituting thecushion material of the invention are equal in terms of spring property,they may be conferred different spring properties after having beendifferently compressed during compression molding. Therefore, it ispossible to provide a cushion material in which different portions havedifferent cushioning abilities and thus in which, when a weight is putthereon, the weight is supported in different manners according to thesites with which it is put into contact. Moreover, it is possible byadjusting the stroke of the male die to allow the mold to have a desiredthickness.

Particularly, the “male die” may be constituted with a base (which formsan element of the cushion material constituting the product) to which aresin molded article with a spring structure can be attached. Then,deliberate preparation of a male die dedicated for the purpose can besafely dispensed with, which will lead to the reduced production cost.Moreover, because part of the product is used as an element (moldingpart) of the molding apparatus, precision of molding will be improved.For raising or lowering the male die, it is preferable to use apantograph type framework. As compared with a hydraulic cylinder orpneumatic cylinder which is used in a conventional apparatus for moldingpolyurethane, the framework in question is so simple that it willcontribute to the reduction of production cost as well as to thesimplification of production facilities. The male die is preferably soconstructed as to forbear a load weighing it or more. If the female dieis made of concrete, it will be possible to safely dispense with the useof a separating agent which would be otherwise required, as well as toreduce production cost as compared with molding where metal dies areused for the same purpose. Moreover, since the molding process itself issimplified, and time required for molding is contracted, mass productionof cushion materials will become possible. Cooling may consist ofspontaneous cooling or forced cooling. Forced cooling is preferablybased on the use of water.

Generally speaking, with regard to the resin molded article with aspring structure as described above, ends of the article tend todisintegrate after molding, and thus require trimming or rounding-offsubsequent to molding, which may be cumbersome. However, with thepresent article with a spring structure, it is possible to trim ends ofthe article after compression molding by cutting and fusion using a heatcutter, and thus to dispense with the trimming process as above, whichreduces superfluous works.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will become apparent fromthe following detailed description of preferred embodiments thereofprovided in connection with the accompanying drawings in which:

FIG. 1 shows a perspective view of a cushion material attached to a base4.

FIGS. 2 a and 2 b show frontal and rear views of the cushion material 1attached to base 4, respectively.

FIG. 3 shows a lateral view of a motor cycle 10 equipped with a seatcomposed of cushion material 1.

FIGS. 4 a and 4 b show perspective views of base 4 viewed from differentangles.

FIG. 5 illustrates a first step of the compression molding applied tothe cushion material 1.

FIG. 6 illustrates the first step of the compression molding applied tothe cushion material 1 viewed from a different angle.

FIG. 7 illustrates a second step of the compression molding applied tothe cushion material 1.

FIG. 8 illustrates the second step of the compression molding applied tothe cushion material 1 viewed from a different angle.

FIG. 9 illustrates a third step of the compression molding applied tothe cushion material 1.

FIG. 10 illustrates a step for attaching the cushion material 1 to abase.

FIG. 11 is a diagram schematically showing steps necessary for producinga resin molded article 30 having a spring structure.

FIG. 12 shows a perspective view of an apparatus for producing a resinmolded article 30 having a spring structure according to the method ofthe invention.

FIG. 13 shows a perspective view of another apparatus for producing aresin molded article 30 having a spring structure according to themethod of the invention.

FIG. 14 shows a perspective view of yet another apparatus for producinga resin molded article 30 having a spring structure according to themethod of the invention.

FIGS. 15 a, 15 b and 15 c show the cross-sections of other resin moldedarticles 30 having a spring structure embodying the invention.

FIGS. 16 a, 16 b and 16 c show the cross-sections of yet other resinmolded articles 30 having a spring structure embodying the invention.

FIGS. 17 a and 17 b show rear and perspective views of a molding die622, respectively.

FIGS. 18 a, 18 b and 18 c show the cross-sections of a resin moldedarticle 30 having a spring structure and of threads 31.

FIGS. 19 a and 19 b show the cross-sections of yet another cushionmaterial 1 embodying the invention.

FIGS. 20 a and 20 b show the cross-sections of yet another cushionmaterial 1 embodying the invention.

FIG. 21 illustrates another embodiment of compression molding necessaryfor molding a cushion material 1.

FIGS. 22 a and 22 b illustrate yet another embodiment of compressionmolding necessary for molding a cushion material 1.

FIGS. 23 a and 23 b illustrate an exemplary compression molding processapplied to a cushion material 1 using a conventional apparatus.

FIG. 24 illustrates another exemplary compression molding processapplied to a cushion material 1.

FIGS. 25 a and 25 b illustrate yet another exemplary compression moldingprocess applied to a cushion material 1.

FIGS. 26 a and 26 b illustrate yet another exemplary compression moldingprocess applied to a cushion material 1 using a conventionalapparatuses.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As is obvious from the reference to a perspective view shown in FIG. 1,and frontal and rear views shown in FIGS. 2 a and 2 b, the cushionmaterial 1 is obtained by preparing a thermoplastic resin (e.g.,thermoplastic elastomer) such as a blend obtained by mixing, forexample, a polyolefin resin such as PE, PP, etc., with VAC, EVA or SBS,and by processing the blend into a resin molded article 30 with a springstructure or a three-dimensional structure, and subjecting the articleor the structure to compression molding.

Explanation of a Resin Molded Article 30 with a Spring Structure

Firstly, the resin molded article 30 with a spring structure will bedescribed.

The resin molded article 30 with a spring structure used in thisembodiment of the invention is a three-dimensional structure havingvoids which is obtained by contacting, entwining, and gathering adjacentones of random loops or curls of continuous and/or short filaments(simply filaments 31 hereinafter) made from the above-described blend.The filaments exist as plural loops and curls (see the inset figure A ofFIG. 1 which enlarges a part of interest). In this embodiment, the resinmolded article 30 with a spring structure comprises hollow filaments 31whose cross-section 31 a is shown in the figure (see the inset figure Bof FIG. 1 which enlarges another part of interest).

In this embodiment, the bulk density of the three-dimensional structuremay be 0.005 to 0.03 g/cm³, preferably 0.008 to 0.03 g/cm³, mostpreferably 0.01 to 0.03 g/cm³. The void ratio of the three-dimensionalstructure may be 96 to 99%, preferably 97 to 99%, most preferably 97 to98%.

Explanation of Cushion Material 1

Next, the cushion material 1 will be described.

The cushion material 1 is obtained by subjecting the resin moldedarticle 30 with a spring structure to compression molding. The cushionmaterial of this embodiment is mainly used as a material of the seat ofan automotive bicycles (e.g., motor cycles 10).

The cushion material 1 has a bilayered structure consisting of two sheetlayers (overlying sheet layer 2 and underlying sheet layer 3). The twosheets may have the same spring property, or different springproperties. The two sheet layers are preferably bonded to each otherwith an adhesive agent or double-faced tape. It is possible to cause thetwo sheet layers or different portions of each sheet layer to havedifferent spring properties by appropriately adjusting the density ofresin molded article 30 with a spring structure, its material, and/orthe diameter of filaments of the article constituting the sheet layers.In detail, the two layers preferably have different spring propertiessuch that, for example, the overlying sheet layer gives a rigid feelwhile the underlying sheet layer a soft feel.

According to this particular embodiment, the overlying sheet layer 2 isless rigid or softer than the underlying sheet layer 3. This is becausethe underlying sheet 3 must be fixed to a base 4 while the overlyingsheet 2 must directly receive the buttock of a rider during riding. Theoverlying sheet 2 preferably has the bulge of its upper surface modifiedto fit to the shape of rider's buttock when the rider takes a ridingposture on the seat. On the other hand, since the underlying sheet layer3 is fixed to base 4, it must be harder than the overlying sheet layer2. The cushion material is preferably constructed such that its shape ismaintained via the hardness of the underlying sheet layer 3.

The cushion material 1 has a characteristic suspension property due tothe underlying sheet layer 3. A conventional seat of an automotivebicycles using urethane foam usually receives a strong counter force(kick back) from the road surface after it exerts a downward spring movetowards the road. To absorb such a counter force, the conventional seatof a motorcycle made from a polyurethane foam often contains coilsprings intimately bonded to the polyurethane foam. However, accordingto this embodiment, the seat has a bilayered structure: the softeroverlying sheet layer 2 is for receiving human weight while the harderunderlying sheet layer 3 is for absorbing downward spring properties.This structural feature can dispense with the use of coil springs.Accordingly, the seat of this embodiment is advantageous in weight andstructure, in simplicity and in that it does not require theintroduction of any special facilities for absorbing downward springproperties. Moreover, the bulk of the seat is comparatively low, andthus the center of gravity lowers, which helps to stabilize the rider'sposture during riding. Further, it is possible by adjusting the strokeof the male die to allow the cushion material 1 to have desiredthickness for its different portions. Thus, it is possible by adjustingthe stroke of the male die to produce cushion materials different insize, shape and profile to meet different suspension requirements.

Since the cushion material 1 is composed of a resin molded article 30with a spring structure, its air permeability is so high that itnaturally rejects the sojourn of moisture. Moreover, if cooled or warmedair transmitted through a duct from an air conditioner is permitted topass through the cushion material of the seat of motorcycle 10, therider can cool or warm his body during riding. If the same equipment isincorporated in the seat of an automotive vehicle, the vehicle can enjoythe state-of-the art function without resorting to any specialfacilities for the purpose.

The shape of the cushion material 1 having a bilayered structurecomprising the overlying sheet layer 2 and underlying sheet layer 3 isnot limited to the one described above with reference to figures, butmay take any shape as desired according to given applications. Forexample, the cushion material 1 may have a single-layered structure.Conversely, the cushion material may have a multiple-layered structurecomprising two or more layers. With regard to a cushion material havinga multiple-layered structure, at least one underlying layer may be madeof a synthetic rubber but at least one of the layers (preferablyoverlying layers) is preferably made of a thermoplastic resin. The shapeof a bulge is not limited to the one described above. The shape, profileand size of a cushion material may be appropriately modified so as tofinely meet given requirements such as product standards, functions, andindividual customers' needs.

It is preferable to place a kilt cushion material composed of a resinmolded article with a spring structure (stitched manually or with asewing machine) over another cushion material having a multiple-layeredstructure (e.g., the overlying sheet layer 2 of cushion material 1), andto use the assembly as a top-sheet of the seat (not illustrated here).In this case, it is possible to confer such subtly undulating bulge thatcan never be observed in the seat prepared based on conventionalmolding, that is, to appropriately modify the shape, profile and size ofcushion materials so as to provide seats that can finely meet givenrequirements such as product standards, functions, and individualcustomers' needs. Thus, it is possible to modify the size, shape andprofile of the seat of motorcycle in accordance with the type of themotorcycle, or the body form of the rider. To put it more specifically,if the seat is for a motorcycle 10 or an automotive vehicle whose user(e.g., professional driver) is strict about driving posture, it ispossible to modify the size, shape and profile of the seat in accordancewith requirements from the user so that the seat can exactly fit to hisdriving posture and performance, which will confer the seat anadditional merit.

Both the overlying sheet layer 2 and underlying sheet layer 3 haveshapes corresponding with that of base 4. As is obvious from inspectionof the perspective views of FIGS. 4 a and 4 b, the base 4 forms abasement of the seat of motorcycle 10. The base 4 has a stopper portion4 a on its frontal side and bulge 4 b on its rear side. The bulge 4 bhas, on its bottom surface, brackets 4 c with which the seat is fixed tothe frame of motorcycle 10. The base 4 has several (e.g., six) cushions4 d made from rubber attached to its bottom surface. Otherwise, manygrooves and holes are formed as shown in the figures.

Apparatus for Producing a Cushion Material 1 and Method Therefor

Next, an apparatus for producing a cushion material 1 embodying theinvention and method therefore will be described with reference to FIGS.5 to 10. A method for producing a resin molded article 30 with a springstructure will be described later.

1) Feeding Step

FIG. 5 shows a lateral view of a system for producing a cushion material1 which is introduced for illustrating a first stage of compressionmolding required for molding the cushion material. FIG. 6 shows afrontal view of the same system for illustrating the first stage ofcompression molding. As seen from inspection of the illustration of FIG.5 or 6, one or more resin molded articles 30 with a spring structure isplaced in a female die 11 made of concrete (simply female die 11hereinafter). At least two resin molded articles 30 may have the samespring property or different spring properties from each other. Asdescribed earlier, each resin molded article 30 is a three-dimensionalstructure having voids obtained by contacting, entwining, and gatheringadjacent ones of random loops or curls of filaments 31 (see the insetfigure C of FIG. 5 which enlarges a part of interest).

According to this production method, it is necessary to heat the resinmolded articles 30 with a spring structure at a temperature exceedingthe softening point of a resin constituting the filaments 31. To achievethis, hot water (preferably having a temperature of 70° C. or higher)from a hot water feeder 13 is allowed to enter into the cavity 12 formedwithin the male die 11, to thereby heat the resin molded articles 30with a spring structure to soften them. Feeding hot water into thecavity of female die 11 is for permitting the hot water to penetrate theresin molded articles 30 and to heat them from inside of the female die11. Alternatively, the female die 11 itself may be heated with a heater.In this case, a heat conductor (e.g., heater) is preferably embedded inthe concrete walls of female die 11. Preferably, the female die 11 arecovered with a thermally insulating material (e.g., with a box made ofwood or of a foaming resin). When it is necessary to heat the air(including the air in the hollow cavities, if the filaments are hollow)contained around filaments 31 constituting the resin molded articles 30with a spring structure, preferably extra heat from the heater embeddedin the concrete walls of female die 11 is used. The hot water feeder 13may be substituted for a steam feeder 17 or the like. When a steamfeeder 17 is used, steam inlets are formed on the wall of the female die11 so that steam can enter the cavity 12 within the die via the inlets.Steam is preferably injected into the die when closure of dies occurs tothereby heat the mold. This mode of heating is preferred because itallows the uniform transmission of a high temperature to the mold. Whenmolding requires pressurization as well as heating, steam heating ispreferred because steam not only heats the mold but also can apply apressure on it. Steam heating is also effective for pressurizing a moldwhile heating it, when the mold has such a complicated structure as toreject uniform pressurization when mechanically pressurized.

Preparation of the female die 11 may be achieved, for example, asfollows. A framework is prepared from an appropriate material such asgypsum or the like. The framework is reversed and fixed on a horizontalplate, a separating agent is applied on the framework or the plate, aconcrete powder is kneaded with water to give a paste, the paste ispoured into the space enclosed by the framework, and the framework isremoved to give a concrete die. Namely, after the concrete paste hashardened, the framework is reversed again to the original position, andthe framework and horizontal plate are removed to isolate a concretefemale die 11. During the preparation process, it is possible by forminga space below the horizontal plate attached to the framework, and byadjusting the height of the space to alter the strength, rigidity andthickness of concrete as desired. For example, to increase the thicknessof concrete, it is only necessary to lower the fixing position of theplate. Since concrete is highly moldable, and easily produces a desiredmold when poured into a framework to be hardened, the production cost ofthe concrete female die 1 is comparatively low ( 1/50 to 1/100 times aslow as the production cost required for a similar die prepared via aconventional die). Concrete further allows the production of femalemolds 11 having complicated shapes, and mass production of the same moldwith improved precision. For example, for molding molds of the samesize, the same master framework can be used repeatedly. Further, sincethe concrete die comes into close contact with a melt, only tightclosure of mating dies allows the formation of a mold each of whichexternal faces is polished as smooth as an abraded surface. If theframework has a negative relief pattern on its inner wall, the patternwill be transferred to the corresponding outer wall of a mold. Or, ifmating dies are closed with a vinyl sheet placed in between, theexternal surfaces of the mold will have an impression reminiscent of thetexture or surface print of the vinyl sheet. Furthermore, since thefemale die 11 is made of concrete, it can safely withstand a highpressure that is applied while a cushion material 1 is molded, and itsdurability is so high as to withstand repeated usage as many as severaltens thousand times moldings. The weight of the female die 11 ispreferably 50 to 100 kg.

The male die 14 is constituted with a base 4 and male platform 14 a (seeFIGS. 4 a and 4 b). The male die 14 is fixed at several points viafixtures to the distal end of a pantograph jack 15. The male die 14,being activated by the pantograph jack 15, mates with the female die 11to thereby apply a pressure from upward onto the resin molded article 30with a spring structure placed in the cavity 12 of the female die 11.The male die 14 is preferably so sturdy as to withstand a pressure of 10t or higher. In this embodiment, a plurality of (e.g., three) pantographjacks 15 are attached to one male die 14. This is for increasing apressure applied to the mold, and for dispersing the applied pressureover plural (e.g., three) sites. The pantograph jack 15 may be operatedmanually, or may be automatically operated being connected to a motor 15a as needed. The proximal end of pantograph jack 15 is fixed to a roof18, and the roof 18 is supported by pillars 19 on the top edges of thefemale die 11. Introduction of the pantograph jack 15 allows thestructure of the system to be simplified which leads to the reduction ofcost. However, the pantograph jack 15 may be substituted for a hydraulicor pneumatic cylinders or the like.

The male die 14 preferably includes, as its element, a base 4 which alsoserves as an element of the product. The base 4 is attached to the maledie platform 14 a with the bottom surface of the former facing to thelower surface of the latter. The upper surface of the male die platform14 a is fixed via joining members to the pantograph jack 15. Since partof the product (base 4) also comprises as an element (male die 14) ofthe molding apparatus, it is only necessary to prepare a female die 11and separate preparation of a male die 14 can be safely dispensed with.With the conventional system for molding polyurethane foams, it isnecessary to prepare male and female dies separately. However, with thesystem operating according to the method of the invention, since part ofthe product serves as an element of male die, preparation of a platenand punch is not needed, which leads to reduced costs and improvedprecision of molding.

2) Die Closing Process

FIG. 7 shows a lateral view of the system for producing a cushionmaterial 1 which is introduced for illustrating a second stage ofcompression molding required for molding the cushion material, whileFIG. 8 shows a frontal sectional view of the same system forillustrating the second stage of the compression molding. As seen frominspection of the illustrations shown in FIGS. 7 and 8, the pantographjack 15 is activated to push the male die 14 (which is acted by the base4) downward as indicated by the arrows in FIGS. 7 and 8, to compress themold. In this particular embodiment, the female die 11 is so adjusted asto allow the male die to enter into the cavity 12 to a deep level.Namely, the female die 11 can be adjusted so as to allow the male die 14to enter into the cavity to a desired level. Since mating of the twodies occurs with a more or less redundancy, it is possible to alter thethickness of cushion material in accordance with a given requirement byadjusting the stroke between the two mating dies. Therefore, with thesame pair of mating dies, it is possible to produce cushion materialshaving various thickness. Needless to say, it is also possible to alterthe density of cushion materials. As described above, with the same pairof mating dies, it is possible to produce various cushion materialsvarying in density, spring property and rigidity by simply adjusting thestroke between the two mating dies as appropriate.

With this system it is possible to freely adjust the thickness of acushion material 1 by adjusting the stroke between the two mating dies.If it is required to produce a thin cushion material 1, it is onlynecessary to reduce the stroke between the two mating dies to a desiredsmall distance. Conversely, if it is required to produce a thick cushionmaterial 1, it is only necessary to increase the stroke between the twomating dies to a desired large distance. Namely, with this system it ispossible to freely adjust the thickness of a cushion material 1. It isalso possible to freely adjust the density, spring property and rigidityof a cushion material. If the tapered angle of the inner lateral wallsof the female die 11 (inner lateral walls of the female die illustratedare substantially perpendicular to the base) is made smaller as neededthan illustrated, it is possible to produce a cushion material whoseprofile has a desired slope angle. The desired slope angle may include,for example, 1/50 to 1/400 (e.g., 1/200). The slope angle may beinwardly or outwardly directed. If the female die 11 has a too largeinward slope angle, it will be difficult to adjust the stroke betweenthe two mating dies to a desired distance. Thus, it is possible usingthe same pair of mating dies to produce various cushion materials 1 inaccordance with given requirements. Particularly, it is possible toproduce the same cushion materials 1 having various desired thickness.For example, it is possible to produce a cushion material in accordancewith a given personal order, that is, to produce cushion materialsfinely meeting personal needs of individual customers. With regard tothe parts of the seat facing the inner thighs of rider, it is preferredto prepare the parts such that they have an enhanced density andrigidity at the cost of spring property. This improves the cushioningproperty and durability of the seat.

Generally, the outline of the seat is determined by the rider's ridingposture, and is more or less constant. However, the thickness of theseat may vary depending on the type (required suspension property) ofthe motorcycle. Thus, it is necessary to adjust the thickness of thecushion material 1 according to the type of the motorcycle. When apolyurethane foam is used as a cushion material, it is processed into amold while foaming. Thus, the mold undergoes uniform expansion duringmolding as long as the same dies are used. Thus, it is necessary toprepare multiple pairs of mating dies if it is required to producecushion materials having different densities and thickness. According tothe production method of this invention, the problems encountered withthe conventional method using polyurethane foams can be safely avoided.

3) Trimming Process

FIG. 9 shows a flat view of the system for producing a cushion material1 which is introduced for illustrating a third stage of compressionmolding required for molding the cushion material. As seen frominspection of the illustration shown in FIG. 9, after the mating diesare kept closed for a certain predetermined period, a heat cutter 16 ismoved along the edges of the male die 14 to remove burrs 32 protrudedfrom the edges of the male die 14 (see the inset figure of FIG. 9 whichenlarges a part of interest) by cutting out those burrs as well asfusing the filament ends of the burrs. According to the conventionalmethod, the mold has its edges trimmed after molding to fit to a desiredsize, which complicates works involved in trimming. However, with themethod of the invention, the mold is easily trimmed. Particularly, sincetrimming is introduced at a stage subsequent to molding, it is possibleto fuse the open ends of filaments of the burrs to prevent theirdisintegration during use, to dispense with the scaling step where themold is tested for its size being as designed, and to simplify testingprocedures subsequent to molding.

4) Mold Separating Process

Cooled water is poured in the cavity 12 of female die 11 to harden theresin molded article 30 with a spring structure. The water is pouredabruptly at one time instead of being slowly poured little by little,which leads to the reduction of time required for hardening. Afterenough time has passed for the mold to harden, the mold is separatedfrom the dies. Whether a given mold hardens or not is determined byslightly relaxing the pantograph jack 15 to see whether there is anyspring-back from the mold. If it is found that there is no spring-backfrom the mold, the mold sufficiently hardens. Then, cycles of alternateheating and cooling the female die 11 and/or resin molded article arerepeated. If a mold is composed of hollow filaments, it is possible toprevent 30 from occurring spring-back by keeping a thermallyequilibrated condition in consideration of the air masses kept in thehollow cavities of filaments.

When the female die 11 is made of concrete, the resin, even if it ismelted, will not adhere to the inner walls of the die which dispenseswith the use of a separating agent. With a molding apparatusincorporating conventional dies, the temperature rises so sharply duringmolding that the resin melt readily adheres to the inner walls of dies.To meet this drawback, when a polyurethane foam is molded, it isabsolutely necessary to use a separating agent which may require extrawork and time. When the mating dies are made of concrete, the moldcontacts so intimately with the walls of dies that it is possible tomass-produce copies having an exactly similar size and shape, eventhough the shape is complicated.

5) Finishing Process

As shown in FIG. 10 which illustrates how a cushion material 1 isattached to a base, an overlying sheet 2 and underlying sheet 3 bothprepared as described above are placed one over another, and theassembly is laid over a base 4. A heat-shaped vinyl leather sheet 5 islaid over the assembly, and fixed to the base 4 with a stapler.Alternatively, fixation of the vinyl leather sheet 5 to the base 4 maybe achieved via an adhesive tape. If the underlying sheet 3 is allowed,during molding, to have indents (or recesses) which engage withcorresponding recesses (or indents) formed on the base 4, it is possiblefor the assembly to be safely fixed to the base without requiring theuse of a stapler or double-faced tape. Layering of the overlying sheet 2on the underlying sheet 3 may be stabilized by inserting a bonding agentor adhesive tape between the two opposite surfaces. Alternatively, thetwo sheets may have indents or recesses on their opposing surfaces whichwill engage with each other when the two sheets are assembled. Then,assemblage of the two sheets does not require the use of a bonding agentor adhesive tape. It should noted, however, that assemblage of theoverlying sheet 2, underlying sheet 3 and base 4 may not require anydeliberate fixation procedure, as far as they are covered with a vinylleather sheet 5 in the finishing process.

Method for Producing a Resin Molded Article 30 with a Spring Structure

An exemplary method for producing a resin molded article 30 with aspring structure as described above will be described.

As shown in the diagrams of FIG. 11, according to the method of thisembodiment for producing resin molded articles 30 with a springstructure, preferably, a polyolefin resin such as PE, PP or the like andanother resin such as VAC, EVA or SBS are fed, in appropriate amounts,via a supplier such as a tumbler, feeder or metering feeder, and thestart resin is dry-blended, mixed, or dissolved in a solvent, kneadedand fragmented into pellets. The powdery mixture or pellets aretransferred to a hopper 21 of an extruder 20.

To be more specific, start resins, e.g., PP and SBS are mixed with atumbler (KR mixer, Kato Scientific Instruments Co.) at 40 rpm for 15minutes.

Next, as seen from the perspective view of FIG. 12, a mixture comprisingthe start resins is poured via a hopper 21 to a uni-axial (axis diameterbeing 65 m) extruder 20. The mixture is melted at a predeterminedtemperature (e.g., 200 to 260° C.), and the melt is kneaded andsubjected to melt-extrusion at a predetermined speed through a pluralityof nozzles, taken off by a winder 23 which will be described later, andformed into solid and/or hollow continuous filaments 31 having apredetermined diameter (e.g., 600 to 90,000 deniers, preferably 3,000 to30,000 deniers, more preferably 6,000 to 10,000 deniers). The filaments31 in a fused state are caused to form loops having a diameter of 1 to10 mm, preferably 1 to 5 mm, and are taken off by the winder within a(water) bath 25 while bringing adjacent ones of the filaments intocontact with each other within the water to be entwined forming randomloops. The contacted and entwined portions of the filaments are at leastpartially fused and bonded to one another. The filaments 31 may comprisesolid filaments and hollow filaments at a predetermined ratio.

The thickness and bulk density of the three-dimensional structure or amass of random loops may be determined as appropriate by adjusting thestroke between take up rolls 24, 24 of the winder 23 in the bath 25. Thethree-dimensional structure (e.g., 10 to 200 mm in thickness and 2,000mm in width) obtained by processing filaments 31 so as to form a mass ofrandom curls or loops, and hardening them in water, is applied toanother pair of take-up rolls 26, 26 to produce a resin molded article30 with a spring structure.

When filaments 31 which have been formed into loops in water are takenoff by the winder 23, the cushion property of the resultingthree-dimensional structure may be altered as appropriate by adjustingthe take off speed of the winder 23. The three-dimensional structure,when it is required to have a comparatively high bulk density, shouldhave a bulk density of 0.03 to 0.08 g/cm³, preferably 0.04 to 0.07g/cm³, most preferably 0.05 to 0.06 g/cm³. The three-dimensionalstructure, when it is required to have a comparatively low void ratio,should have a void ratio of 91 to 97%, preferably 92 to 96%, mostpreferably 93 to 94%.

In taking off the filaments, the take-off speed of the winder 23 isadjusted to a low take-off speed at intervals of e.g., 3 to 5 m by e.g.,reducing the take-off speed of take up rolls 24, 24 to a lowpredetermined level at certain predetermined regular intervals. Then, itis possible to obtain a resin molded article 30 with a spring structurecomprising a series of alternate high-density portions and low-densityportions repeating at regular intervals (e.g., 30 to 50 cm) in alongitudinal direction, the high-density portions being formed whenfilaments are taken off at a low take-off speed while the low-densityportions being formed when filaments are taken off at a high take-offspeed.

As seen from the frontal view of FIG. 13, if it is expected that athree-dimensional structure such as a resin molded article 30 with aspring structure will hardly be bent by the take-up rolls 24, 24, it ispossible to adjust the take-off speed of the winder as above to producea three-dimensional structure comprising a series of high-densityportions and low-density portions, and to adjust the winder system suchthat the three-dimensional structure can be bent at their low-densityportions. The resin molded article 30 with a spring structure obtainedvia the above-described processes are cut with a cutting device 27 intopieces having a desired length. The bath 25 is equipped with inlet andoutlet valves (not illustrated here).

As seen from the frontal view of another apparatus shown in FIG. 14where a cutting device 127 is placed in a water bath 125, the cuttingdevice 127 is put below a winder 123, and a transport device 128comprising a conveyor carrying multiple joining spikes on its surface isplaced in the water bath 125 opposite to the winder. The conveyorcarries spring structure pieces obtained by cutting a three-dimensionalstructure at predetermined sites by piecing joining spikes into thepieces and thereby capturing them on its surface. The elementscorresponding with those of the foregoing embodiment are represented bysimilar numerals with, however, 1 being attached to the third place ofthe numerals.

By a method as described above, a resin molded article 30 having aspring structure is obtained which has, for instance, a bulk density of0.03 g/cm³ and thickness of 50 mm. The three-dimensional structure canbe manufactured by using sub-structures which include one type ofproperty or a combination of a plurality of types of propertiesdifferent from each other. For the details of how resin molded articles30 with a spring structure are actually produced by the aforementionedmethod, and results of the tests performed on them, the readers arereferred to EP 00-1-182-826AI and others which were published by thepresent Inventors.

Other Embodiments of Resin Molded Articles 30 with a Spring Structure

Resin molded articles 30 with a spring structure representingembodiments other than the foregoing ones will be described below. Theirmolding is based on the viscosity of start resins.

During molding of a resin molded article 30 with a spring structurementioned below, it is possible to obtain a three-dimensional structurewhich comprise portions different in cushion property by adjusting thetake-off speed and heating temperature. For example, it is possible toobtain a resin molded article 130 with a spring structure as shown inFIG. 15 a where the cushion property is weakened gradually or atpredetermined regular intervals as a testing probe advances from theperiphery to the core. In this particular example, the periphery isconstituted with a hard portion 130 a while the core with a soft portion130 b. This distribution of cushion property may be reversed as seenfrom a resin molded article 230 with a spring structure shown in FIG. 15b where the core is constituted with a hard portion 230 a while theperiphery with a soft portion 230 b. It is also possible to obtain aresin molded article with a spring structure where spots having adifferent cushion property (for example, two spots) are dispersed in thearticle as seen from the one 330 shown in FIG. 15 c.

A resin molded article with a spring structure like the one 130 issuitable as a cushion material of the seat of a motorcycle 10. Since thecushion material 1 has hard lateral surfaces, they adequately fit to themedial bulges of the rider's thighs when the rider mounts on the seatand takes a riding posture, which leads to stable driving. A resinmolded article with a spring structure like the one 230 is suitable as amaterial of a helmet. A single three-dimensional structure of which thesurface (contacts with the scalp) is soft while the core is rigidenables the production of caps (sun hats and helmets) which will notdisturb the hair style. Such a cap is preferable because it prevents thepenetration of sun beams but permits excellent air permeability.

The cushion material of a seat may achieve its assigned function as longas it has a sufficiently rigid external surface, depending on the weightapplied on the seat and bending it undergoes when loaded with theweight. In such a case, it is possible to obtain a resin molded articlewith a spring structure by preparing plural thin three-dimensionalstructures each having a different density, and laminating them in anappropriate combination into a single layered structure, instead ofpreparing a single three-dimensional structure which comprises portionshaving different densities. This method permits the amount of resinsused for preparing a spring structure to be saved, and improvesproductivity. For example, it is possible to obtain a resin moldedarticle with a spring structure 430 shown in FIG. 16 a, by preparing athree-dimensional structure 430 a, placing another structure 430 bhaving a lower bulk density below it, and placing a second structure 430c having a yet lower bulk density below the former, and bonding thethree structures into a single layered structure.

It is also possible to obtain a resin molded article 30 with a springstructure 530 shown in FIG. 16 b which is partially reinforced withcavities 530 a (partition blocks) which are formed in the structure byheating the spots to melt away filaments there. Formation of cavities530 may be achieved prior to or subsequent to compression molding. It isalso possible to obtain a resin molded article 30 with a springstructure as shown in FIG. 16 c where each cavity includes a clamp 530 blike a metal brace. The clamp 530 b may be inserted into the cavityprior to or subsequent to compression molding.

The diameter of filaments 31 constituting a resin molded article 30 witha spring structure is not necessarily uniform. Even if a single cushionmaterial is used as a seat, the weight imposed on a given portiondiffers depending on which part of the seat the portion occupies.Enhancing the rigidity of a given portion can be achieved by alteringthe bulk density of that portion as well as by modifying the diameterand/or hardness of filaments constituting the portion. For example, itis preferable to distribute thick and/or rigid filaments to a portionwhich comes into contact with the rider's buttock and sustains a largepart of his weight during riding.

To produce a spring structure where one portion (e.g., central portion)comprises more thick filaments than the remaining portions, the moldingdie 622 has nozzles prepared as shown in FIG. 17 a such that nozzles 622a corresponding to the central portion have a larger diameter than theremaining nozzles 622 b. If this molding die 622 is used, thickfilaments 631 are extruded from its central portion together with normalthin filaments 31 extruded from the remaining portions as shown in FIG.17 b. It is possible to obtain a spring structure where the rigidity isaltered in a complicated manner, by using such a molding die asdescribed above.

It is also possible to obtain a cushion material which comprisesfilaments having the same thickness and bulk density with those of acomparable structure but is softer or harder than the comparablestructure, by employing a filament material different from what is usedin the comparable structure. For example, if the cushion material 1 isused as the seat of a motorcycle 10, it is possible to employ adifferent filament material in accordance with the weight of a user,which will increase the marketing value of the seat.

It is also possible to entwine filaments of a spring structure withnatural fibers or metal wires to thereby produce a complex springstructure. By so modifying the filaments of a spring structure, it ispossible to improve, for example, the thermal resistance, collapsingtendency under prolonged use, and tensile strength of filaments, thatis, weak points inherent to synthetic resin filaments. For example, itis preferable to entwine filaments 731 with plural metal wires 733 asrepresented in a resin molded article 730 with a spring structure shownin FIG. 18 a. It is also preferable to combine hollow filaments 731 withmetal wires by not only entwining the former with the latter, butinserting the latter through the cavity of the former as shown in asectional view of a combined filament of FIGS. 18 b and 18 c.

Cushion Materials 1 Representing Other Embodiments

When a female die 11 and male die 14 are closed to compress a mold toproduce a resin molded article 30 with a spring structure, it ispossible to alter the heating temperature in a stepwise manner tothereby produce a spring structure in which the rigidity changes fromone portion to another. For example, it is possible to produce a cushionmaterial 101 as shown in FIG. 19 a where a lower portion 101 a(plate-like portion) is rigid while an upper portion 101 b is soft. Theedges 101 c are preferably heated to be formed into rigid plate-likeportions. For example, edge portions 101 c where filament ends arecurled by heating are preferably processed to take a plate-like formduring trimming. The edge portions 101 can snugly mesh with thecorresponding edges of a base 4. Preferably, prior to assemblage, theedge portions 101 c are expanded, and allowed to return by springproperty, to thereby mesh with the corresponding edges of the base. Thisarrangement allows the cushion material to be attached to the basewithout requiring the use of a stapler, or to be detached from thelatter.

When a female die 11 and male die 14 are closed to compress a mold toproduce a resin molded article 30 with a spring structure, the femaledie 11 may be hotly burnt so as to raise the temperature of the die tosuch a high level as to melt the surface of a mold which, when hardened,forms a hard skin covering the mold (epidermis molding). With thismethod, it is possible to melt and harden only the superficial skin 201a of a mold or resin molded article 30 with a spring structure as seenfrom a cushion material 201 of FIG. 19 b, which will dispense with latercoating (e.g., coating with a vinyl leather 5). This method is alsoapplicable for molding an instrument panel using a resin as a material.Namely, according to this method, it is possible to not only prepare amold but also form a hard superficial skin around the mold.Particularly, if a cushion material 1 must be water-proof or insolubleto solvents, or must have a protective coating, the epidermis moldingbased on hot burning is preferably employed to form the superficial skin201 a.

Since the cushion material 1 constituted with a resin molded article 30with a spring structure of this embodiment is highly air-permeable, itis more preferable depending on given applications to dispense with theuse of a vinyl leather 5 than to cover the cushion material 1 with theleather. If the use of a vinyl leather is omitted, a resin moldedarticle 30 with a spring structure is preferably covered with a net 306as seen from the cushion materials 301 shown in FIGS. 20 a and 20 b. Thenet 306 may be applied over the cushion material 301 after compressionmolding. The net 306 is preferably made of a water-repellent material(e.g., plastics). Then, the net 306 can maintain its excellent airpermeability, and thus the seat is conveniently used even when the areais humid or the time is a wet season. Particularly such a seat issuitably used when incorporated in a buggy which usually runs on a sandyland. The net 306 prevents the disintegration of a cushion material 301so effectively that it improves the durability of the seat. The meshdensity of the net 306 is not limited to the one shown in the figure,but may be set to any desired level. A vinyl leather sheet 5 may beapplied over the net-covered cushion material. This is because, when theseat is incorporated in an electric train and is damaged intentionally,the seat can be prevented from the entry of foreign objects.

Mating Dies Representing Other Embodiments

In the above embodiments, the female die 11 is placed downward while themale die 14 placed upwards, but positioning of the two dies may bereversed. If the reverse positioning is adopted, the female die 11applies its weight on a mold during molding, and thus compressionmolding is achieved via pressures imposed by a compressor as well as viathe weight of the female die. Both the female die 11 and male die 14 arepreferably made from concrete, metal or FRP (fiberglass reinforcedplastics). If the heavier die is placed upward (pressing side) andallowed to mate with the opposite die placed downward, it is possible toexploit the weight of the upper die for compression molding. Forexample, compression molding may be achieved by placing one die madefrom heavier concrete upward, and the other die made from lighterconcrete downward, or by placing one larger die upward and the otherlighter die downward.

This embodiment incorporates a pantograph jack 15 to quickly apply auniform pressure on a mold. However, if compression molding is achievedexploiting a pressure due to the heavier weight of a die placed upward,it may be possible to dispense with the use of a pantograph jack 15. Forexample, according to a molding system as shown in FIG. 21, a male die114 is suspended with balancers 115 or the like each comprising a springmaterial, and compression molding is achieved by allowing the male die114 to fall into the female die 111 due to its own weight as indicatedby the arrows of the figure. Alternatively, the male die 214 may beconnected via a hinge 215 to the female die 211 as shown in FIG. 22. Themale die 214 is opened to a predetermined angle, a resin melt is pouredinto the cavity within the female die 211, the male die is moved asindicated by the arrow of the figure until it closes the cavity withinthe female die 211, and thus compression molding is achieved byexploiting the weight of the male die 214.

FIGS. 24 to 26 concern with other embodiments. With the systems shown inthose figures, vertical positioning of the female die and male die maybe reversed. With the systems, the concrete female die 11 placed upwardsserves as a weight during compression molding. If the apparatuscomprises a female die 111 suspended with balancers 115 made of a springmaterial, compression molding may be achieved by allowing the female die111 to engage with the male die 114 due to its own weight as indicatedby the arrows of the figure. Alternatively, the male die 214 may beconnected via a hinge 215 to the female die 211 as shown in FIG. 22. Themale die 214 is opened to a predetermined angle, the male die is movedas indicated by the arrows of the figure until it closes the cavitywithin the female die, and thus compression molding is achieved byexploiting the weight of the female die 211 in mating with the male die214.

Although it was mentioned above that the female die 11 is preferablymade of concrete, it is possible to utilize a conventional apparatusadapted for molding polyurethane foams as profitably as the apparatus ofthe invention if the dies are modified such that their trimming marginscan be increased, and accommodate the expansion of a mold as a result ofmolding, as shown in FIGS. 26 a and 26 b. For example, according to aconventional system, start resins (liquids) are poured into the cavity,and an upper die 314 and lower die 314 are mated to be closed and theresins are allowed to foam in the cavity (foaming as a result of themixture of two resins). However, the apparatus may be modified asfollows: a resin molded article 30 with a spring structure is placed inthe cavity, the article is compressed by mating the two dies, and burrsprotruded from the mating dies are removed via pressures generated as aresult of intimate closure of the two mating dies. Then, it will bepossible to obtain a cushion material 1 like the one representing anembodiment of the invention without resorting to a apparatus whichincorporates concrete-made mating dies. Or, it is preferable to trim amold with a heat cutter after the upper die has been removed. The matingdies 311, 314 of a conventional apparatus may be made from a metal suchas iron. The die is preferably made from concrete or metal, but may bemade from a complex synthetic resin material such as FRP.

As shown in FIGS. 26 a and 26 b, it is possible to employ part (e.g.,lower die 311) of a conventional apparatus. For example, according to aconventional apparatus, start resins (liquids) are poured into thecavity, and an upper die (not illustrated) and lower die 311 are matedto be closed and the resins are allowed to foam in the cavity (foamingas a result of the mixture of two resins). Instead, a resin moldedarticle 30 with a spring structure is placed in a apparatus, and it maybe compressed by mating a male die 314 with a lower die 311 equippedwith a base 4.

The temperature of atmosphere or temperature control is important forcompression molding. During molding, start resins soften andintermingle. However, the mixture does not occur at molecular levelsbecause the resins do not melt completely. Thus the air masses entrappedin a mold are the same with those existent in the start resins. Toproperly form a mold, it is necessary for the temperature of the airmasses to be equilibrated with the softening temperature of startresins. Otherwise, if the heightened temperature is abruptly reduced toa far low level, the air masses will expand which will causespring-backs to impair proper molding, unless mating of the two dies ismaintained so as to keep the equilibrium state.

INDUSTRIAL APPLICABILITY

As described above, according to the invention, it is possible toquickly produce a cushion material constituted with a resin moldedarticle with a spring structure which has desired resistances to imposedweight and impact. Mass production of such a cushion material is alsopossible. Since the production of such cushion materials is based oncompression molding, it is possible to freely modify the size and shapeof individual products. If the cushion material is expected to beexposed to vertical vibrations, horizontal vibrations or complexvibrations, it is possible to confer bulges and recesses on both sidesof a cushion material such that the cushion material can effectivelyabsorb vibrations as much as possible.

According to the method of the invention, since burrs are cut as well asfused with a heat cutter which is moved along the edges of a male moldduring closure of the two mating dies, trimming is quite easy.Particularly, since trimming is introduced at this stage of molding,disintegration of open filaments at the edges is safely prevented, andrenewed trimming and scaling subsequent to molding which would beotherwise required can be safely dispensed with, which reduces worksrequired for after-molding treatment.

Further, since a base to which a resin molded article with a springstructure is attached also acts as a male die, it is necessary toprepare only a female die for proper molding which will lead to reducedproduction costs. Furthermore, since the product itself is utilized asan element of the molding apparatus, precision of molding will beimproved.

Since it is possible using a molding apparatus incorporating a singlepair of mating dies according to the invention to produce a cushionmaterial in which some portions have a different thickness from that ofother portions. Thus, with a single apparatus, it is possible to producevarious cushion materials different in size, shape and density inaccordance with individual requirements without resorting to multiplepairs of dies. More specifically, it is possible, when it is required toprovide seats appropriate for the type of motorcycles, to provide seatswhose thickness varies depending on the type (required suspensionproperty) of the motorcycle. For example, according to the method of theinvention, it is possible when it is required to provide thin cushionmaterials, to adjust the molding apparatus such that the stroke betweenthe two mating dies becomes thin. Conversely, when it is required toprovide thick cushion materials, it is only necessary to adjust themolding apparatus such that the stroke between the two mating diesbecomes wide. Thus, it is possible to produce cushion materials inaccordance with given personal orders, that is, to produce cushionmaterials finely meeting personal needs of individual customers.

Furthermore, according to the method of the invention, it is possible toreadily produce cushion materials different in property including theirthickness by simply adjusting the stroke interval between the two matingdies and choosing an appropriate material (e.g., in filament diameter,texture, bulk density and void ratio). More specifically, according tothe method of the invention, it is possible with a single apparatus toproduce various cushion materials different in size, shape and densityin accordance with individual requirements without resorting to multiplepairs of dies. For example, it is possible, when it is required toprovide seats appropriate for the type of motorcycles or automotivevehicles, to provide seats whose thickness varies depending on the type(required suspension property) of the motorcycle or automotive vehicle.Further, according to the method of the invention, it is possible toprovide cushion materials in which the distribution of spring propertiesand rigidities is adjusted as desired by simply varying the stroke widthbetween the two mating dies, without modifying the physical propertiesof the cushion material itself. For example, when a cushion material isused as a material of the seat of a motorcycle or automotive vehicle, itis possible to modify the cushion property of the cushion material inaccordance with the type of motorcycle (for touring, road racing ormotocross) without resorting to any complicated processes which wouldotherwise be required. If the cushion material is used as a material ofthe seat of a motorcycle for motocross, it may be prepared so as toabsorb the weight of a rider. Then, the rider can steer the motorcyclewhile resting on the seat which will insure stability during riding.

If the cushion material comprises two or more layers of sheets, it ispossible to readily alter the properties of the cushion material bychoosing appropriate constitutive resin molded articles with a springstructure (in terms of, e.g., diameter of filaments, material, bulkdensity, void ratio, etc.) or by adjusting the stroke width between thetwo mating dies. For example, combination of spring properties betweenthe overlying layer and underlying layer can be altered as desiredwithout resorting to any complicated processes: it is quite easy tocombine overlying and underlying layers having the same spring property,as well as to combine an overlying layer having a certain rigidity withan underlying layer having a lower rigidity. It is also possible tocombine overlying layers with underlying layers such that there isformed a stepwise stroke between adjacent layers to thereby produce acentral ridge.

Therefore, it is possible to provide seats that can finely meet givenrequirements such as product standards, functions, and individualcustomers' needs, which will leads to the increased value of theproduct. Thus, when the cushion material is used as a material of theseat of a motorcycle or automotive vehicle, it is possible to modify theseat in accordance with the type of the motorcycle or automotivevehicle, or the body form of the rider. To put it more specifically, ifthe seat is for a motorcycle or automotive vehicle whose user (e.g.,professional driver) is strict about driving posture, it is possible tomodify the seat in accordance with requirements from the user so thatthe seat can exactly fit to his driving posture and performance. If thecushion material is used as a material of the seat of a motorcycle formotocross, it may be prepared so as to absorb the weight of a rider.Then, the rider can steer the motorcycle while resting on the seat whichwill insure stability during riding.

According to the method of the invention, cushion materials are moreeasily produced than polyurethane foams undergoing secondary processingaccording to the conventional method. Although in manufacturing apolyurethane foam, toxic materials such as TDI and the like are used, aresin molded article of the present invention can be produced withoutgenerating toxic gases and hence insures good working conditions.

According to the method of the invention, resins such as PE or the likemay be recycled into edible oil containers of thermoplastic resins orbiodegradable plastic films for agricultural use with an additionalmerit added. Cushion materials made of a resin molded article with aspring structure themselves may be repeatedly recycled by melting usedcushion materials and submitting the melt again to molding process. Theresin molded article according to the invention is so excellent inrecyclability that it will not act as an undue load to environments evenif it must be disposed of after use. Further, the resin molded articleaccording to the invention can be manufactured at reduced costs sincerecycled resins can be used for producing the same.

The cushion material of the invention made of a resin molded articlewith a spring structure is highly durable and resistant to collapsingeven after prolonged use, has a very small quantity of local sinking,and does not give a feeling of touching a hard bottom, and verticalswing. Moreover, the cushion material, when a user sits on it, uniformlyreceives the weight of the user on a whole region in contact with thecushion structure. Hence, the cushion material causes less fatigue ofthe user than a polyurethane foam-made cushion, and makes the user feelmore relaxed. Thus, the cushion material of the invention can give acharacteristic relaxed feeling to the user that can hardly be obtainedfrom a polyurethane foam-made cushion.

The cushion material of the invention made of a resin molded articlewith a spring structure has such an excellent spring property that, whenit is used as a material of the seat of an automotive vehicle ormotorcycle, it will dispense with the use of coil springs which havebeen installed beneath the conventional seat of an automotive vehicle ormotorcycle to absorb kick-backs from the road surface which would beotherwise a nuisance to the driver. This simplifies the structure of theseat, and lowers the center of gravity, which helps to stabilize thevehicle or motorcycle during running.

Since the resin molded article of the invention has a structure havingcompletely continuous voids, it is so excellent in air permeability thatit does not keep extra moisture. if cooled or warmed air transmittedthrough a duct from an air conditioner is permitted to pass through thecushion material of the seat of motorcycle, the rider can cool or warmhis body during riding. Since the cushion material is resistant to waterand will not degenerate when soaked with water, it may be profitablyused as a material of the seat of a motorcycle. The cushion material maybe washed with water, and will readily dry even when washed with water.

As described above, the method of the invention for producing a cushionmaterial composed of a resin molded article having a spring structure issuitably used for providing a cushion material composed of a resinmolded article with a spring structure, that is, a material suitablyused as a supportive element of any supports on which one can sit, restor mount such as seats of automotive vehicles, motor cycles, bicycles,electric trains, and aircraft, saddles for horse riding, chairs, sofasand beds, regardless of whether the seat is exposed to vibrations or notas a substitute for a conventional polyurethane foam-made cushionmaterial.

If the cushion material is used as a supportive element of a seat whichis expected to receive no vibrations during use, it is only necessary tosubject one surface of the cushion material to compression molding. Onthe contrary, if the cushion material is used as a supportive element ofa seat which is expected to receive vigorous vibrations during use, forexample, the seat of an automotive vehicle or motorcycle, it ispreferable to overlap two or more cushion materials each comprisingkilted resin molded article with a spring structure.

If the molding apparatus uses, for compression molding, a pantographjack instead of a hydraulic unit, the apparatus can have a simplerstructure which will reduce production costs. Moreover, with thisapparatus, it is easier to adjust the stroke width between mating dies.

The embodiments of the present invention are not limited to thosedescribed above, but may permit many variations and modifications withinthe technical scope of the invention. Also, since certain changes may bemade in the above construction without departing from the scope of theinvention, it is intended that any variations of and equivalents to theforegoing embodiments shall be interpreted as included in the technicalscope of the invention.

Thus, the broadest claims that follow are not directed to a machine thatis configuration a specific way. Instead, said broadest claims areintended to protect the heart or essence of this breakthrough invention.This invention is clearly new and useful. Moreover, it was not obviousto those of ordinary skill in the art at the time it was made, in viewof the prior art when considered as a whole.

Moreover, in view of the revolutionary nature of this invention, it isclearly a pioneering invention. As such, the claims that follow areentitled to very broad interpretation as to protect the heart of thisinvention, as a matter of law.

It will thus be seen that the objects set forth above, and those madeapparent from the foregoing description, are efficiently attained. Also,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatters contained in the foregoing description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween. Now that theinvention has been described;

REFERENCE NUMERALS

-   -   1: cushion material    -   2: overlying sheet    -   3: underlying sheet    -   4: base    -   5: vinyl leather    -   10: motorcycle    -   11: female die    -   12: cavity    -   13: hot water feeding device    -   14: male die    -   15: pantograph jack    -   16: heat cutter    -   20: extruder    -   21: hopper    -   22: molding die    -   23: winder    -   24: take-off rolls    -   25: bath    -   26: take-up rolls    -   27: cutting device    -   30: resin molded article with a spring structure    -   31: filament    -   32: burr

1. A method for producing a cushion material composed of a resin moldedarticle having a spring structure, comprising the steps of: forming athree-dimensional structure with voids at a predetermined bulk densityby contacting, entwining, and gathering ad] acent ones of random loopsor curls of solid and/or hollow continuous filaments and/or shortfilaments made from a thermoplastic resin; heating a male die or afemale die, or a female die and/or the three-dimensional structure to atemperature sufficiently high to soften the three-dimensional structure;allowing the male die to intimately contact with the female die so as totightly compress the three-dimensional structure; and hardening thethree-dimensional structure by cooling.
 2. A method as described inclaim 1 for producing a cushion material composed of a resin moldedarticle having a spring structure wherein: superfluous edges protrudedfrom the three-dimensional structure into the stroke between the twomating dies are cut with a heat cutter so that the edges are cut out andopen ends of edge filaments are fused together.
 3. A method as describedin claim 1 for producing a cushion material composed of a resin moldedarticle having a spring structure wherein: a base to which the resinmolded article with a spring structure is attached serves as a male die,and the male die is allowed to intimately contact with a female die soas to tightly compress the three-dimensional structure; and thethree-dimensional structure is hardened by cooling.
 4. A cushionmaterial composed of a resin molded article having a spring structureobtained by overlapping two or more layers of sheets each comprising athree-dimensional structure having a same or different spring property,wherein: the three-dimensional structure is formed by contacting,entwining, and gathering adjacent ones of random loops or curls of solidand/or hollow continuous filaments and/or short filaments made from athermoplastic resin; and the three-dimensional structure is heated in amale die or in a female die to a temperature sufficiently high to softenit, compressed via closure of the two mating dies, and allowed to hardenby cooling.
 5. A cushion material as described in claim 4 composed of aresin molded article having a spring structure wherein the springproperty is determined by the density, material and/or filament diameterof the three-dimensional structure.
 6. A cushion material as describedin claim 1 composed of a resin molded article having a spring structurewherein the volume of the resin molded article with a spring structurecan be altered by adjusting stroke of the male die when the female diehas a deeply set receptive base.
 7. A cushion material as described inclaim 1 composed of a resin molded article having a spring structurewherein, out of the two mating dies, at least the female die is madefrom concrete.
 8. A concrete-made female die used for molding a resinmolded article with a spring structure which is obtained by preparing aframework according to a master female die effective for molding a resinmolded article with a spring structure, pouring concrete paste into thespace within the framework, and allowing the concrete paste to harden.9. A cushion material as described in claim 1 composed of a resin moldedarticle having a spring structure wherein the vertical movement of atleast one of the two mating dies is achieved by a pantograph jack.
 10. Acushion material composed of a resin molded article having a springstructure comprising a three-dimensional structure, wherein: thethree-dimensional structure is formed by contacting, entwining, andgathering adjacent ones of random loops or curls of solid and/or hollowcontinuous filaments and/or short filaments made from a thermoplasticresin; and the three-dimensional structure has, on both its top andbottom surfaces, two or more bulges formed on predetermined linear areasby stitching the boundaries of each area using a thread of athermoplastic resin, and shortening the thread by pressure.
 11. A methodfor producing a cushion material composed of a resin molded articlehaving a spring structure, comprising the steps of: extruding a melt ofa thermoplastic resin into filaments and contacting, entwining, andgathering adjacent ones of random loops or curls of continuousfilaments, thereby forming a three-dimensional structure containingvoids at a predetermined bulk density; cutting the periphery of thethree-dimensional structure or a resin molded article with a springstructure to give a U- or V-shaped profile, and stitching the thusformed edges with a thread of a thermoplastic resin; and stitching witha thread of a thermoplastic resin the boundaries of predetermined linearareas on the top and bottom surfaces of the three-dimensional structure,and shortening the thread by pressure.
 12. A method as described inclaim 11 for producing a cushion material composed of a resin moldedarticle having a spring structure, comprising the steps of: placing thethree-dimensional structure on a female die; heating the female dieand/or the three-dimensional structure to a temperature sufficientlyhigh to soften the three-dimensional structure; allowing a male die tointimately contact with the female die so as to tightly compress thethree-dimensional structure; cooling the three-dimensional structure toconfer a constant spring property thereto; and stitching with a threadof a thermoplastic resin the boundaries of predetermined linear areas onthe top and bottom surfaces of the three-dimensional structure, andshortening the thread by pressure.